The subject of the invention is a suction jet pump with an improved suction action. Suction jet pumps are used, for example, in fuel tanks of motor vehicles, in order to convey fuel out of one region of the fuel tank into another region.
Suction jet pumps are nowadays employed in fuel tanks of motor vehicles and are therefore known. They have the task of conveying fuel out of distant and lower regions of the fuel tank to the feed unit or into a baffle. The suction jet pump consists, in this case, essentially of a propulsion jet tube, an intake orifice and a mixing tube. The liquid quantity supplied to the suction jet pump via the propulsion jet tube emerges under pressure from the propulsion jet nozzle delimiting the propulsion jet tube and subsequently enters the mixing tube. The intake orifice for the liquid to be conveyed is arranged between the propulsion jet nozzle and the mixing tube. The propulsion jet entering the mixing tube generates a vacuum upstream of the latter, so that the liquid to be conveyed is sucked into the mixing tube via the intake orifice. The efficiency of a suction jet pump, in this case, depends on many factors. Thus, for example, the length of the mixing tube and other geometric factors influence the efficiency. The general disadvantage of suction jet pumps is their relatively low efficiency of about 20 to 30%.
It is known that a good suction action is achieved if the mixing tube length amounts to more than ten times the mixing tube diameter. On account of the conditions of space in a fuel tank, however, precisely these geometric requirements often cannot be implemented, so that the efficiency, which is low in any case, is impaired even further.
The object on which this invention is based is, therefore, to provide a suction jet pump with improved suction action, which has a simple design and does not take up a large construction space.